Table Of ContentRETARGETABLE COMPILER TECHNOLOGY
FOR EMBEDDED SYSTEMS
Retargetable Compiler
Technology for Embedded
Systems
Tools and Applications
by
Rainer Leupers and Peter Marwedel
University of Dortmund
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.
A C.I.P. Catalogue record for this book is available from the Library of Congress.
ISBN 978-1-4419-4928-8 ISBN 978-1-4757-6420-8 (eBook)
DOI 10.1007/978-1-4757-6420-8
Printed on acid-free paper
All Rights Reserved
© 2001 Springer Science+Business Media Dordrecht
Originally published by Kluwer Academic Publishers, Boston in 2001
No part of the material protected by this copyright notice may be reproduced or
utilized in any form or by any means, electronic or mechanical,
including photocopying, recording or by any information storage and
retrieval system, without written permission from the copyright owner.
To Carl and
Veronika, M alte,
Gesine, and Ronja
Contents
Preface ix
1. INTRODUCTION 1
1.1 Embedded systems and their characteristics 1
1.2 Efficient hardware 3
1.3 Efficient software 4
1.3.1 How to specify embedded system software? 4
1.3.2 Efficient compilers 5
1.3.3 Retargetable compilers 6
2. COMPILERS IN EMBEDDED SYSTEM DESIGN 9
2.1 Design flow and hardware/software codesign 9
2.2 Design space exploration 11
2.2.1 Levels in the design space 11
2.2.2 Algorithm selection 14
2.2.3 Options for implementing algorithms 15
2.2.4 Process mapping and HW /SW partitioning 15
2.2.5 Memory system design 17
2.2.6 Instruction set options 18
2.2.6.1 Design of VLIW machines 18
2.2.6.2 Design of non-VLIW machines 21
2.2.6.3 Word length optimization 21
2.2.6.4 Register file sizing 23
2.2.7 Micro-architectural options 24
2.3 Design verification 26
3. SOME COMPILER TECHNOLOGY BACKGROUND 27
3.1 Front end 28
3.2 Intermediate representation 34
3.3 Backend 40
3.3.1 Code selection 40
vii
viii RETARGETABLE COMPILER TECHNOLOGY
3.3.2 Scheduling 44
3.3.3 Register allocation 50
3.3.4 Address code optimization 53
3.3.5 Phase coupling issues 56
3.3.6 Peephole optimization 58
4. HISTORICAL OVERVIEW 59
4.1 Contributions from the compiler community 59
4.1.1 UN COL 59
4.1.2 Code generation for expressions 60
4.2 Contributions from microprogramming 61
4.2.1 Motivation 62
4.2.2 Early work 62
4.2.3 First retargetable microcode compilers 63
4.2.4 The MIMOLA project 64
5. RETARGETABLE COMPILER CASE STUDIES 67
5.1 Retargetable compilers for GPPs 68
5.1.1 GCC 68
5.1.2 LCC 71
5.1.3 Marion 75
5.1.4 PAGODE 76
5.1.5 SUIF /Machine SUIF 77
5.1.6 Zephyr/VPO 79
5.1.7 LANCE 81
5.2 Retargetable compilers for DSPs 84
5.2.1 CBC 84
5.2.2 REDA CO 87
5.2.3 CodeSyn/FlexW are 89
5.2.4 SPAM 91
5.2.5 RECORD 95
5.3 Retarget able compilers for VLIWs 98
5.3.1 ROCKET 98
5.3.2 IMPACT 99
5.3.3 Trimaran 100
5.3.4 Trimedia 102
5.3.5 AVIV 103
5.3.6 Mescal 105
5.4 Retargetable compilers for ASIPs 105
5.4.1 MSSQ 105
5.4.2 PEAS 110
5.4.3 Valen-C 113
5.4.4 EXPRESS 114
5.4.5 BUILDABONG 116
5.5 Special retargetability techniques 118
Contents ix
5.5.1 Code generation methods 118
5.5.1.1 Balakrishnan's microcode compiler 118
5.5.1.2 Mavaddat's formal language approach 119
5.5.1.3 Langevin's automata theoretic approach 119
5.5.1.4 Romer's automata theoretic approach 120
5.5.1.5 Wilson's ILP based code generator 121
5.5.1.6 FACTS 122
5.5.1.7 Bashford's CLP based code generator 123
5.5.1.8 Yamaguchi's code generator 125
5.5.2 Retargetable compilers for microcontrollers 125
5.5.2.1 Krohm's compiler 125
5.5.2.2 SDCC 126
5.5.3 Code generator generators 126
5.5.3.1 IBURG 126
5.5.3.2 OLIVE 129
5.5.3.3 BEG 131
5.5.4 Assembly-level optimization 132
5.5.4.1 SALTO 132
5.5.4.2 PROPAN 132
5.5.5 LISA 134
5.5.6 Compilers for industrial reconfigurable cores 137
5.5. 7 Retarget able test program generation 138
5.5.8 Retargetable estimation 139
5.5.9 Miscellaneous 140
5.6 Commercial retargetable compilers 141
5.6.1 CoSy 141
5.6.2 CHESS 142
5.6.3 Archelon 145
5.6.4 ucc 147
6. SUMMARY AND OUTLOOK 149
Appendices 152
Tabular overview of compiler tools 153
References 155
About the authors 171
Index
173
Preface
Embedded systems are information processing systems embedded in
larger products. They have their own characteristics which make them
different from desktop systems. For example, they have to be imple
mented efficiently, and the same holds for the increasing amount of em
bedded software. Designing an efficient, software- and processor-based
system requires that optimized processors are used. Such an optimiza
tion requires a careful analysis of the design space, including a study of
cost/performance tradeoffs. In order to avoid assembly language pro
gramming for such studies, compilers are needed. For analyzing the
effect of design options on the performance, these compilers should be
capable of generating code for all potential hardware configurations.
This is possible with retargetable compilers. Such compilers can be
adapted to new hardware easily. Recently, many new approaches for
designing such compilers have been developed. This book presents an
overview and classification of these techniques. For each of the compilers,
we mention key features, limitations, as well as software availability. The
list of retargetable compilers covered has never been collected before.
We also introduce key terms and techniques for compiler construction,
explain where in the design flow retargetable compilers fit and present
a history of retargetability. For people starting work on compilers for
embedded systems, this book should save a significant time for finding
references.
The book is self-contained and requires only fundamental knowledge
in software design. It is intended to be a key reference for researchers
and designers working on embedded software, compilation, and processor
optimization. It can also be used by people who need to get an overview
quickly, such as consultants and advisors. Please enjoy reading this
book!
RAINER LEUPERS, PETER MARWEDEL
xi
Chapter 1
INTRODUCTION
Writing this book was motivated by the growing usage of a large vari
ety of processors in embedded systems. This trend has to be reflected in
the corresponding development of still missing tools for the design of em
bedded systems. In order to understand the requirements for such tools,
we will first of all have to look at the characteristics of the application
areas that we are considering.
1. Embedded systems and their characteristics
Embedded systems can be defined as information processing systems
which are integrated into larger systems. In such systems, information
processing is usually not directly visible to the user, and customers will
typically not buy a certain product -like a car or a mobile phone- be
cause he or she is interested in the features of the information processing
equipment. For example, customers will not buy a certain model of a
mobile phone because of the brand name and the clock speed of the
processor contained in the phone. They buy it because of the function
ality that it provides, regardless of the electronic system supplying part
of that function. The same applies to information processing in cars,
trains, airplanes and smart homes, to mention some other examples of
embedded systems.
In many cases, the customer does not even recognize that information
processing takes place, partly because the standard interfaces for PC-like
equipment -like mice, keyboards and screens- are typically not available
for embedded systems. Rather, push buttons and small displays are used
as user interfaces.
1
2 RETARGETABLE COMPILER TECHNOLOGY
Tools for the design of embedded systems are very much influenced by
the characteristics of embedded systems. What are those characteristics
? The following list contains some of the most relevant ones:
1 Embedded systems have to be efficient. One of the most notable
instances of this is the need for energy efficiency, which applies at
least to all portable embedded systems.
Mobile phones and personal digital assistants are a very good exam
ple for this. They use orders of magnitude less energy than today's
desktop computers and battery lifetime is a key argument for selling
these systems.
Energy consumption has also to be considered in the case of cars.
Customers expect cars to be operational even after many weeks of
not using them. Hence, the energy consumption of parked cars has
to be extremely low.
Weight is another aspect of efficiency. From looking at the mobile
phone market (as well as at the laptop market) it becomes obvious
that customers prefer light-weight systems.
Silicon area is also very important, since many embedded systems
have to be small and have to be fabricated at competitive prices.
Many embedded systems -especially multimedia and communication
systems- have very high performance requirements. These require
ments have to be met with the least amount of resources.
Progress in process technology might lead to less emphasis on the
efficient use of silicon area and processor performance. However,
progress in battery technology is expected to be slow. Hence, the
importance of low energy consumption can be expected to increase
in the foreseeable future.
2 Embedded systems are using an increasing amount of software.
Only some peripheral components are implemented with special pur
pose hardware. The main reason for this is the flexibility of software,
enabling a short time to market, late design changes and easy pro
duct upgrades. For most application areas, current processors are
fast enough to meet performance requirements. Also, customers ask
for more and more functions and these can be provided in software
much easier than in special purpose hardware.
As a result, it has been found that, for many application areas, the
amount of software in embedded systems is doubling every two years
[43].
